On the use of plant cellulose nanowhiskers to enhance the barrier properties of polylactic acid

Abstract

Polylactic acid (PLA) nanocomposites were prepared using cellulose nanowhiskers (CNW) as a reinforcing element in order to asses the value of this filler to reduce the gas and vapour permeability of the biopolyester matrix. The nanocomposites were prepared by incorporating 1, 2, 3 and 5 wt% of the CNW into the PLA matrix by a chloroform solution casting method. The morphology, thermal and mechanical behaviour and permeability of the films were investigated. The CNW prepared by acid hydrolysis of highly purified alpha cellulose microfibers, resulted in nanofibers of 60-160 nm in length and of 10-20 nm in thickness. The results indicated that the nanofiller was well dispersed in the PLA matrix, did not impair the thermal stability of this but induced the formation of some crystallinity, most likely transcrystallinity. CNW prepared by freeze drying exhibited in the nanocomposites better morphology and properties than their solvent exchanged counterparts. Interestingly, the water permeability of nanocomposites of PLA decreased with the addition of CNW prepared by freeze drying by up to 82% and the oxygen permeability by up to 90%. Optimum barrier enhancement was found for composites containing loadings of CNW below 3 wt%. Typical modelling of barrier and mechanical properties failed to describe the behaviour of the composites and appropriate discussion regarding this aspect was also carried out. From the results, CNW exhibit novel significant potential in coatings, membranes and food agrobased packaging applications.

Development of Starch Biofilms Using Different Carboxylic Acids as Plasticizers

“…An important alternative is the use of biodegradable polymers, which can be degraded by microorganisms such as bacteria, fungi or algae. Natural additives such as starch, cellulose and lignin are used in conventional formulations of the plastics 1 . Starch is an abundant raw material which allows the development of recyclable products.…”

Composites of High-Temperature Thermomechanical Pulps and Polylactic Acid

“…The limited crystallization of PLA in injection molding can cause the impairment of mechanical properties (Harris and Lee 2008;Drieskens et al 2009;Sanchez-Garcia and Lagaron 2010), but our data indicate that the introduction of fibers speeds up the crystallization process in the used experimental setup. Transcrystallization, the formation of oriented crystals at the fiber-matrix interface, has been found to dominate in PLA/wood flour composites, where the fiber surface is rough (Mathew et al 2006).…”

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Vpliv dodatka nanofibrilirane celuloze na mehanske lastnosti poli(3-hidroksibutirata)

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“…12 V prvem primeru pridobimo transparentne filmske strukture z navadno izbolj{animi bariernimi in mehanskimi lastnostmi. 11,13 Mo`nosti uporabe nanokompozitov, izdelanih po drugem postopku predelave so precej bolj raznolike, ker jih je mogo~e oblikovati v najrazli~nej{e profile oziroma kon~ne izdelke. Po drugi strani je izdelava nanokompozitov s tehnologijo ekstruzije veliko bolj zapletena kot pri tehnologiji vlivanja in trenutno predstavlja {tevilne izzive na raziskovalnem podro~ju.…”